Using this as the intermediate XML representation for fields allows us to
write generic field functions and then different functions for producing
actual HTML. See, for example, fieldsToTable and fieldsToPlain.

High-level form post unwrappers

This function wraps around runFormPost and fieldsToTable, taking care of
some of the boiler-plate in creating forms. In particular, is automatically
creates the form element, sets the method, action and enctype attributes,
adds the CSRF-protection nonce hidden field and inserts a submit button.